With improving medical technologies, and a growing as well as aging world population, both the number of surgical operations and their complexity increase. Take just the eye, for example, millions more elderly patients each year undergo various ophthalmic surgeries including cataract extraction, intraocular lens replacement, cosmetic blepharoplasty, entropion, ectropion and tear duct repair. Younger patients also increasingly seek LASIK correction of myopia and astigmatism. More infants also undergo strabismus or amblyopia (lazy-eye) correction. As a result, many tens of millions of eye surgeries occur each year following which the operated eye needs to be protected in the weeks following eye surgery from pressure injury and receive liquid topical medications several times daily. This is especially critical following “open globe” operations (such as cataract surgery, because accidental pressure can lead to rupture of the globe, and partial or total loss of vision). Similarly, following accidental injury to the eye (from foreign body to chemical splashes) the injured eye is typically covered and protected for a period of time with multiple daily administration of topical medication.
All of the above post-operative or post-trauma care of the eye currently requires an uncomfortable rigid metal or plastic discoid fenestrated eye shield to be taped in place over the periorbital area. The disc is ovoid in shape and measures 1 mm to 3 mm thick, depending on material. The discoid shield and the adhesive tape holding it in place must be removed multiple times each day for medication administration. The edge of the eye shield compresses uncomfortably against the bony prominences underlying the eyebrow and cheek, and the absence of a seal between the shield and the skin precludes taking a shower or simple washing of the head or face. The fenestration of the discoid shield is to diminish the amount of light coming into the photosensitive eye, or to allow the patient to see, depending on the personal circumstance of the patient.
Even more annoying, and uncomfortable to the point of pain, is the peeling back of the tape holding the eye shield to administer medication several times a day. This tedious and unpleasant process is aggravated by the discomfort of peeling adhesive tape off eyebrows and sensitive facial skin. Elderly patients are especially susceptible to the associated problems and complications because they have thin atrophic skin and brittle capillaries that bruise easily, their vision is already impaired and they often do not have skilled live-in help to assist with properly dressing the eye and administering the medication multiple times each day. This situation threatens patient compliance, and both the quality of post-operative eye care and surgical outcome. The repeated peeling of adhesive tape removes the buffering layer of dead squamous cells and brings fresh adhesive into proximate contact with microcapillaries, t-cells and histiocytes. This incites tissue irritation or allergic reaction to the tape adhesive. Lastly, the eye shield and associated tape is visually unattractive and draws unwanted attention from on-lookers.
Also difficult is the precise delivery of liquid eye medication to oneself. It is difficult to judge:
1) when the medicine dropper is positioned properly over the eye (such that the medication does not land outside of the eye margins and the expensive medication is wasted), or
2) when the tip of the eye drop dispenser is too close to the eye (which would risk contamination of the dispenser tip and risk abrasion injury to the cornea).
A variety of other eye patches are disclosed in prior teachings, most comprising of soft padded ovoid patches, some with an inflatable bladder or intermediate pocket for inserting extra padding or compress. These prior art all require changing with each medication delivery, do not protect the eye from water (as while taking a shower), and with the exception of the hard discoid shield, do not protect the injured eye against external pressure.
Turning attention now to examples of other types of wounds, this invention further pertains to 1) contaminated wounds, 2) chronic decubitus wounds and 3) wounds from plastic and reconstructive surgery.
The cornerstone to wound management is maintaining a clean, sterile and optimized environment for healing, including good oxygenation, nutrition and vascular flow. Many wounds are “dirty” from traumatic injury or from infection superimposed on underlying disease processes (such as diabetic peripheral vasculopathy, other co-morbidities or malnutrition) that renders the body incapable of dealing with the extent of tissue compromise and growing microbial load.
In a blast injury, as might be sustained by a soldier, an enormous load of soil organisms is forced deep into tissue, which then feeds and multiplies on the extensively damaged tissue. This is a very challenging category of wounds to clean and heal. Perhaps the most challenging wound of all is the chronic decubitus wound because the underlying vascularity that determines tissue viability is often substantially compromised. Wounds from plastic and reconstructive surgery may entail skin grafts or tissue pedicles that have tenuous vascularity, must be protected from outside shear force (unintended movement upon the graft tissue, such as during dressing change) and need an optimum, highly protected environment for healing.
Wound closure involves the migration of epithelial and subcutaneous tissue from the wound periphery toward the center. A good blood supply, aided by the normal activation of a variety of immune system cells is important to the healing process. However, the larger or more infected the wound is, the greater is the disruption of the original blood supply. This translates to a greater degree of local edema, microstasis, hypoxia and hypoperfusion; all increasing the likelihood of wound deterioration and infection.
Whenever the wound is not clean, wound debridement is an essential precursor to wound closure. It is the removal of necrotic tissue, exudate, and metabolic waste from a wound and improves the healing process. It reduces the bio-burden of the wound; controls and potentially prevents wound infection, especially in deteriorating wounds; and allows the physician to visualize the wound walls and base to assess viable tissue. Exudate usually results from infection. Staphylococcus aureus, for example, is known to produce a fibrin-rich biofilm that is resistant to the body's natural immune response to foreign bodies. Residual necrotic tissue not only impedes wound healing, but can also result in generalized infection, osteomyelitis, septicemia, loss of limb, or even death. Removing the necrotic tissue will help restore circulation and oxygen delivery to the wound, both critical to healing. Wounds at sites of rich blood supply, such as the scalp, heal faster and are less prone to infection. Oxygen is required for energy-dependent metabolic processes, production of free radicals that kill bacteria, and proliferation of cells, such as fibroblasts and epithelial cells, which are crucial for wound healing. Bacterial overgrowth under hypoxic conditions may compete with the healing tissue for nutrients and produce exotoxins and endotoxins that could damage newly generated and mature cells.
Hypoxic conditions in dirty wounds also encourage anaerobic bacterial growth which is serious, potentially life-threatening and difficult to treat. Hyperbaric oxygen chambers are available in certain tertiary medical centers and therapy time is limited to a few hours due to oxygen toxicity. Medical problems commonly treated with hyperbaric oxygen therapy include non-healing wounds, osteoradionecrosis, acute carbon monoxide poisoning, acute gas embolism, burns, and certain infections. Yet, medical use of hyperbaric oxygen must be applied conservatively because of the potential risk of toxicity to the central nervous system (seizure) and lungs. These problems and resource scarcity belie the enormous cost of proper wound care: $20 billion annually in the US just for chronic wound care in nursing homes. An estimated 1.2 million people with diabetes suffer from lower extremity ulcers each year, and of all the foot amputations in the United States, 84 percent, or 60,000 amputations, are related to diabetic foot ulcers. Proper and timely wound care can significantly reduce the incidence of such tragic outcome. The teachings of this invention will help curtail the costs and complications of wound care.
Debridement may also be required to prepare the wound bed prior to application of new biomaterials used to treat chronic wounds, such as cultured keratinocytes and a bioengineered human skin equivalent. As these modalities are used more extensively in clinical practice, selecting the appropriate debridement option will become more critical.
Because necrotic and devitalized tissue range from moist, yellow, green, or gray tenacious plaques to thick, leathery black eschar if the wound dehydrates, its removal can pose a challenge. In addition to posing a barrier to oxygen and nutrients, it can also serve as a breeding ground for microbes, and may mask underlying buildup of fluid or abscesses.
Several types of debridement are available. Mechanical methods include wet and dry dressings, whirlpool, and pulsed lavage. It is labor intensive, may be painful and nonselective because it does not discriminate between viable and nonviable tissue. Newly formed epithelium can also be removed by these methods.
Chemical debridement methods, including topical use of enzymatic gels and solutions can dissolve necrotic tissue from the wound. Various types of enzymes target specific components of dead tissue, such as fibrin and collagen. Enzymes that act on necrotic tissue are categorized as proteolytics, fibrinolytics, and collagenases. Enzymes for wound debridement are mostly formulated as ointments, solutions absorbed by a wet gauze, hydrocolloids, or hydrogels. The efficacy depends on the enzyme employed, with fibrinolysin ointment regarded as ineffective, collagenase ointment somewhat effective, and papain-urea ointment most effective. Because the interface or contact between the enzymatic dressing and necrotic substrate has to be manually changed and refreshed, a prolonged time is required for these treatments to deliver significant improvement. This ranges from four days to three weeks with daily wound treatments for fresh ointment supply (especially during the first week).
A laboratory study on rabbits and mice by Yaakobi et al and published in July in Wounds 16(6):201-205, 2004, reported that by continuously dripping proteolytic enzyme solutions such as bromelain, collagenase, papain, pepsin, protease and trypsin in suitable medium, they were able to vastly shorten the debridement time. The authors concluded, “The feasibility of this approach was demonstrated on lab animals by studies on skin treatment and wound debridement. Our results have clearly demonstrated technical feasibility and efficacy of streaming of enzyme solution. The time required for effective treatment was on a scale of a few hours, substantially shorter than the several days/weeks required for treatment with enzyme-containing ointments. The authors, however, gave no suggestions how to bring this laboratory finding to clinical application, and to contain the continuous enzyme solution run-off if applied at the bedside in a clinical setting.
Lastly, biological methods of wound debridement including maggots of the blowfly, Phaenicia sericat, and certain leeches have also been shown to be effective in debriding certain types of wounds. However, confining them within the wound site can pose a challenge and when they wander outside the wound onto adjacent normal skin, a creepy-crawly sensation is unpleasant for the patient. It is therefore also an aspect of this invention to provide methods wherein such creatures can be easily confined in a closed space and their distracting sensation upon the patient minimized.
Recent advances in general wound therapies have included the application of continuous suction to the underside of a wound dressing. It is believed that such treatment helps to reduce tissue edema, enhance drainage and fibroblast cell migration. While negative pressure appears to accomplish the above, the advanced wound chamber system disclosed herein will provide a yet more advanced system of wound care and therapy as never before available. This includes automated cycles of enzymatic debridement, wound lavage, irrigation with antimicrobials and immune modulators, optimization of microenvironment with the infusion of high-concentration oxygen, nitric oxide, cyclical application of positive and negative pressure to simulate physiologic circulation and accelerate wound healing. These methods, devices and special features will be disclosed in detail below.